I am not sure what you want to do with what output the metter?.
The simplest instrument will be a current clamp and next a dual channel scope.

Click to expand...

Well, I have a project on Meter Reading. I want to implement a simple kilowatt meter. So that the output can be fed into MCU.
current clamp and next a dual channel scope? Sounds interesting, further explanation?
Thanks

I don't think that wuold work for AC power. The calculation is a bit involved because you have to take RMS value and power factor into consideration. There are plug-in power meters available for home appliances, have a look and see if you could tap the output somehow. Be careful though!

Other route would be to develop your own. There are power measuring chips available with different sensors and outputs options. Analog Devices, Motorola and TI have them.